Thread: Ducting update.

"Please describe your invention."

"Err, its a plastic box, an Occky strap and a floor drain"

"Anything else?, no gerbils, whipped cream or drain pipes?"

"No. . . . . . Ah yes, wait there is a sort of a fat rubber hose"

"I see, and what category would you say this falls under?"

"Dust removal?"

"More like bull dust removal sir!, . . . . be a good chap and move along. . . . . NEXT!"

Right ?! Where's the problem ![emoji848][emoji3]

I presume you have to move the box, to lock the router, every time you make a height adjustment. Do you find that time consuming?

Originally Posted by Lappa

I presume you have to move the box, to lock the router, every time you make a height adjustment. Do you find that time consuming?

Yes its a bit of a PITA but when I get the "through the table height adjustment" setup it shouldn't be so bad although if you want to lock router height (which I usually do ) then its a take the box off every time. Not that much slower than opening an enclosure though.

I'm not a big router table user - probably only use it about once a month.

Got enthused about attending to the belt side of the sander DC.

The main problems have been
- dust has been shooting past the end of the dust collection port at the end of the belt , see red arrows below.
- lots of dust settling out under the belt.

The shooting over the top issue did not change much even after I opened up the port size to that show,
I put this down to the entrance of the rectangular hood (even after modification) being too close to the belt so it could not gather enough air.

oldBeltPort.jpg

I had no idea why so much dust would end up under the belt but my guess was it was from dust sticking to the belt and dropping off as it goes around.

So this is what I have come up with.
A bell mouth hood for 100 mm ducting would nominally have 2 x 50mm radius edges.and so would be 200 mm wide and be 50 mm deep or thick.
About 15 mm of extra depth is needed to allow for attachment of the hood to ducting so a thickness of 50 +15 = 65 mm of MDF.
Using 18 mm MDF needs 4 layers so this one is 72 mm deep. The extra depth is put into additional tapering so this is why this looks more like a trumpet

Throat.jpg
One thing I will have to do is put some sort of a coarse grill in that maw before it swallows up smaller pieces being sanded

Here is a side on view so you can see the adjustable bracket that holds the BMH.
The bracket is currently using cheap Hex socks machine screws but I will replace those with screw handles.
Posn1.jpg
I could immediately tell that although this setup captured the dust shooting straight off the top of the belt, it still did not stop dust from being dragged around by the belt and being deposited under the sander.
To attack this I add a stainless steel air deflector plate to about the 5 o'clock position which disrupted the air very close to the belt and that substantially reduced the amount of dust falling out underneath the belt, but then the deflector plate also deflected some of the dust away from the sides of hood.

So then I moved the hood back and down and this seems to give the best dust collection
Sideonview.jpg

Now there is still a problem with this setup and that is when dealing with long pieces so that you want to go over the top of the end roller.
To do that I have to move the hood even further back and down.

Even at this this distance the hood seems to work nearly as well especially for thin stock and using the middle third of the belt..

OTTop.jpg

Nice mods.
Bob have you ever experimented with an "air knife" blowing across the belt to strip off the dust so it can be captured by the dust hood?
Pete

Originally Posted by QC Inspector

Nice mods.
Bob have you ever experimented with an "air knife" blowing across the belt to strip off the dust so it can be captured by the dust hood?
Pete

No I haven't but I was thinking of doing exactly what you describe this last night. I like the name - could be a good way to keep the belt clean too.

Provided the CFM of the knife was well below the hood it should not scatter the dust too far.

I just realised the plan I put up for the rocker gate is not quite right, The radii of curvatures have to be drawn around the rotational points of the 3 gates parts.
If you use the plans on post 11 there will be a few excess bits and pieces that all need to be cut off to make it work.


Here are the plans that will align correctly.
Unfortunately it can not be cut out of the same circle of material (well it could but the circle would need to be of a larger diameter)
Rocker1.jpg




If like said above don't cut out the major holes until you have made the complete sandwich all boled together.
Then with the rocker over to one side drill a pilot hole thru the position of the hole and mark the holes using the pilot hole.

These plans suit PVC or MDF, if Al is used they can be made considerably tighter/closer/narrower all round.

Originally Posted by BobL

No I haven't but I was thinking of doing exactly what you describe this last night. I like the name - could be a good way to keep the belt clean too.

Provided the CFM of the knife was well below the hood it should not scatter the dust too far.

Exair is a company that has a lot of compressed air products including air knives. You might poke around their site for ideas. They do seem to need lots of compressed air though.

Pete

Originally Posted by QC Inspector

Exair is a company that has a lot of compressed air products including air knives. You might poke around their site for ideas. They do seem to need lots of compressed air though.

Pete

Thanks for the lead Peter - very interesting stuff. My mining engineering brother told me about these some time ago - they were using them on ore conveyor belts

I wasn't thinking of a continuous stream of air but using something like either a pedal switch controlled by the operator to only supply air when the sanding or a timed burst device - also mentioned on the Exair site),
Something like the unit I use to auto vent my compressor tank would be ideal.
ie 1 2" 2 Way Automatic Electronic Timed Air Compressor Drain Tank Valve 220V | eBay

The little unit I have cost a whopping $30 inc postage from China and has vent times of 0.5 - 10 seconds every 30 s up to 45 min.
In 0.5 secs the 1000 fpm 2m long belt goes around 1.25 times so something like a 1 second burst every 10 seconds would probably do.
This would cut the air use dramatically

I also have a couple of ideas about making the knife edge - sounds like my sort of project and it seems like it has application in a lot more than cleaning belts.

In the slider/rocker component the dimensions d and e are reversed for the 100 mm ducting.

Atholjax

Originally Posted by atholjax

In the slider/rocker component the dimensions d and e are reversed for the 100 mm ducting.

Atholjax

Well spotted - all fixed now.

The thumbnail has the same error.

Originally Posted by atholjax

The thumbnail has the same error.

. and the new one should be